A U.S. federal investigator probing alleged Russian interference in the 2016 U.S. presidential election asked Deutsche Bank (DBKGn.DE) for data on accounts held by President Donald Trump and his family, a person close to the matter said on Tuesday.

Germany's largest bank received a subpoena from Special Counsel Robert Mueller several weeks ago to provide information on certain money and credit transactions, the person said, without giving details, adding that key documents had been handed over in the meantime.

Deutsche Bank has lent the Trump Organization hundreds of millions of dollars for real estate ventures and is one of the few major lenders that has given large amounts of credit to Trump in the past decade. A string of bankruptcies at his hotel and casino businesses during the 1990s made most of Wall Street wary of extending him credit.

Mueller is investigating alleged Russian attempts to influence the election, and potential collusion by Trump aides. Russia has denied U.S. intelligence agencies' conclusion that it meddled in the election and Trump has said there was no collusion with Moscow.

A U.S. official with knowledge of Mueller's probe said one reason for the subpoenas was to find out whether Deutsche Bank may have sold some of Trump’s mortgage or other loans to Russian state development bank VEB or other Russian banks that now are under U.S. and European Union sanctions.

Holding such debt, particularly if some of it was or is coming due, could potentially give Russian banks some leverage over Trump, especially if they are state-owned, said a second U.S. official familiar with Russian intelligence methods.

“One obvious question is why Trump and those around him expressed interest in improving relations with Russia as a top foreign policy priority, and whether or not any personal considerations played any part in that,” the second official said, speaking on the condition of anonymity.

Yeah. Well, we already know that they were working overtime with several different actors including Felix Sater and the Agalarovs to build that Trump Tower in Moscow even as Trump was running for president. That actually should be enough to cause the congress to launch a full-scale inquiry into the possibility of Trump's corrupt practices. (I know, lol. Simply imagine for a moment if Clinton had had such dealings during the campaign.)

Mueller is well within his purview looking at Trump's transactions with Russia. I would just point out once again that all prosecutors have the ability to pursue any crime he or she comes across during an investigation. One can only imagine the possibilities in Trump's finances. He burned all his bridges with legitimate lenders decades ago.

Trump warned Mueller that looking into his personal finances is a red line so I'm going to guess there will shortly be a clamor to fire him for over-stepping his bounds. Of course, firing Mueller is already something Trump is thinking about every minute of the day anyway. I suspect it's only a matter of time before he pulls the trigger.